Precast Deck Research Articles

Nondestructive Radiographic Evaluation and Repairs to a Prestressed Concrete Parking Structure Following Partial Collapse

This paper presents use of radiographic imaging (X-ray) in evaluation of existing reinforcing steel and tendon configuration of a structure following a collapse and development of steel retrofit and carbon-fiber-reinforced polymer (CFRP) repairs. A collapsed section in the driving surface in a precast concrete parking deck prompted an engineering evaluation and survey of the entire deck for assessment and repairs to distressed members. Distress was identified in decking members and perimeter spandrel beams in varying forms and degrees. Repairs to the decking members involved supporting the distressed decking using supplemental steel retrofit brackets installed through the double-Tee stems containing prestressing tendons. The precise location of the tendons in the stems needed to be identified to implement this repair in order not to damage the tendons during drilling for through-stem anchors. Radiographic X-ray imaging in this application enabled locating and avoiding the tendons in the stems to support and strengthen the decking member. The supplemental steel brackets also enabled continued and improved operation of an existing expansion joint in the area of repair. Radiographic evaluation technique was also used in identification of steel reinforcement configuration in the perimeter spandrel beams exhibiting cracking at bearing locations with maximum shear. Radiographic exposures were used for evaluation of existing steel configuration and development of CFRP repairs. CFRP repairs were implemented in perimeter spandrel beams while decking surfaces were retrofitted with steel brackets to support the driving surfaces and enable continued expansion and contraction in the existing expansion joints.

Ultra-high-performance concrete connections for precast concrete bridge decks

Ultra-high-performance concrete connections for precast concrete bridge decks

Shear Transfer Mechanism and Design of Shear Connectors for Full-Depth Precast Deck Panel System

The development and implementation of full-depth, precast overhang panel systems has the potential to improve constructibility, productivity, and make bridges more economical. Recently, various shear connector systems have been proposed to provide shear-transfer resistance between girders and the precast overhang panels. There is, however, limited information and guidance on the design for shear-transfer capacities for full-depth, precast overhang panel systems. This research performed experiments and assessed the results to estimate the shear-transfer capacities of four types of shear connectors systems. The confinement system of the shear pocket was varied with the hopes of enhancing the sheartransfer capacity. Results indicate that five stages of shear-transfer and failure mechanisms occur during testing. These stages include initial adhesion loss, shear key action, shear key action failure, dowel action of the shear connectors at a sustained load, and final failure of the system. Results from this research indicate that steel reinforcing hoops placed in the shear pocket and shear reinforcing hoops placed in the overhang panel around the opening of the shear pocket provide limited or no improvement in capacity of the shear connector/coupler system. When comparing energy absorption capacities, however, the shear connector systems evaluated can provide improved performance when compared with the conventional R-bar system. A new equation is proposed based on this research.

Performance of stud clusters in precast bridge decks

A new design approach to clustered stud shear connection in composite bridges with precast decks is required to accommodate highly concentrated shear force in small area. Shear connection of the prefabricated slab consists of stud connectors, mortar in a shear pocket and reinforcement around the pocket. More general design approach for the shear connection is provided by relative strength between shear strength of shear connectors, bearing strength of mortar in shear pockets, and the shear strength of precast deck. Considering the relatively high strength mortar in the bearing zone of the shear connection this paper deals with structural performance of stud clusters to simplify the connection details. In a shear pocket, closer stud spacing than the current pitch requirement was considered. Push-out tests were conducted to evaluate the ultimate strength according to expected failure modes. The main parameters of the test were stud spacing and confining details. In order to use group arrangement of stud connectors, it is necessary to prevent premature failure of bearing zone by strengthening the shear connection using confining reinforcements. An empirical equation of ultimate shear strength of the shear connection was proposed to consider the effect of stud spacing when the spacing is less than five times stud diameter. Fatigue tests showed that the fatigue endurance of clustered stud connectors with spacing of more than three times stud diameter can be evaluated using current design codes.

Transverse panel-to-panel connections for full-depth precast concrete bridge deck panels on continuous steel girder bridges: Part 1, experimental

The focus of this article is the performance measurement of transverse panel-to-panel connections for full-depth concrete bridge deck panels on continuous steel girder bridges. Using a simulated HS 20 vehicle loading, two nonprestressed and four posttensioned connections are tested cyclically in negative bending. Testing objectives include the determination of the net service stress limit required to control cracking and prevent leaking under service load moment. Results find cracking and leaking to occur for connections with 170 psi of initial stress and no leaking or full-depth cracking for connections with 340 psi. The superior performance of the connections with higher prestress leads the authors to recommend the specification of a maximum net tensile stress of 3√fc.

Bridge Constructed with GFRP-Reinforced Precast Concrete Deck Panels: Case Study

AbstractLong-term monitoring of two precast deck panels constructed with glass fiber–reinforced polymer (GFRP) bars and six girders of a single-span bridge is reported. Each instrumented panel is 12.5 m long, 2.1 m wide, and 235 mm thick; all panels in the bridge are reinforced with GFRP bars. Static truck-load test results are discussed and observations are made regarding the overall response of the bridge. The deflections of the girders to known static loads and AASHTO distribution factors are evaluated. Data from loads applied to the bridge were collected remotely for approximately 3 years and analyzed. Collected data also include concrete strains in the deck panels and relative displacements of the panels with respect to the girders. The response of the girders and bridge deck is evaluated by comparing test results to design requirements as well as to finite-element analyses. It is shown that, after 3 years in service, the performance of the bridge including the precast concrete deck is well within de...

A Study on the Flexural Performance of UHPC Precast Deck-Joint Interface by the Exposure of Steel Fiber

As a solution against the serviceability problem caused by the cracks occurring at the UHPC precast deck-joint interface, this study proposes a method exposing the steel fiber at the interface and evaluates the corresponding flexural performance of the lap spliced construction joint. After having slowed down the strength development of the concrete placed in the joint of the precast deck by means of a curing retardant, the concrete at the interface is crushed so as to expose the steel fibers and the change in the flexural performance is observed experimentally according to the exposure of the steel fibers. The results show that, even if the ultimate strength and stiffness of the UHPC precast deck including the joint are mostly determined by the arrangement details of the rebar lap splice, the exposure of the steel fibers can secure stable ductile behavior and reduce the width of the cracks generated at the precast deck-joint interface under service load.

Transverse panel-to-panel connections for full-depth precast concrete bridge deck panels on continuous steel girder bridges: Part 2, time-dependent analysis

In this article, the authors seek to determine the initial compressive stress to avoid cracking and leaking in precast, prestressed concrete bridge deck panels. They use an age-adjusted effective modulus method to evaluate time-dependent stress redistribution in composite systems. The evaluation found an initial precompression of 200 to 300 psi to be adequate for single span bridges, 200 to 700 psi for three-span bridges, and 100 psi for two-span bridges. They also determine that accelerated construction schedules for continuous span bridges make it necessary to substantially increase initial compressive stress.

Mackenzie River twin bridges:North America’s largest field-cast ultra-high performance concrete connections project

This article profiles the Mackenzie River Twin Bridges project, the largest field-cast ultra-high performance (UHPC) project in North America in terms of bridge size and total volume of UHPC joint fill material used. Part of the TransCanada Highway realignment near Thunder Bay, Ontario, Canada, The Mackenzie River bridges consist of twin two-lane bridges with three spans each (total length 590ft (180m)). The bridges use variable depth, continuous steel plate girders with full-depth precast, lightly prestressed concrete deck panels. This article presents a detailed examination of the project, which also includes precast concrete approach slabs and concrete deck panels connected at transverse joints and attached to steel girders using field-cast ultra-high-performance concrete.

Lifting of GFRP Precast Concrete Bridge Deck Panels

AbstractThe Beaver Creek Bridge on U.S. Highway 6 is a single-span bridge and a pilot project for glass fiber–reinforced polymer (GFRP) precast bridge decks in Utah using accelerated bridge construction (ABC). The Utah Department of Transportation decided to evaluate GFRP bars as an alternative to steel bars for reinforcing the bridge deck. The precast concrete panels were 12.62-m long, 2.08-m wide, and 235-mm thick and were reinforced entirely with GFRP bars. The bridge deck panels were lifted from the underside at four points using steel cables inside steel tubes or nylon straps instead of embedded steel anchors. Two of the 24 panels used to construct the bridge deck were instrumented with strain gauges. Experimental strain measurements showed that the panels exhibited acceptable levels of strain that were below concrete cracking limits. By comparison, similar laboratory panels with identical thickness and reinforcement that were lifted with four embedded anchors from the panel top experienced cracks on...

Diseño automático de tableros óptimos de puentes de carretera de vigas artesa prefabricadas mediante algoritmos meméticos híbridos

This paper deals with the minimum cost automatic design of precast bridge decks made of U-beams and an upper slab. It uses a hybrid memetic algorithm that combines the population search of solutions by genetic algorithms and a search by variable neighborhood. This algorithm is applied to a bridge made of two isostatic U-beams of 20-40m of span and a width of 12m. This example has 40 discrete variables. The evaluation module takes into account the service and ultimate limit states usually considered for these structures, i.e. flexure, shear, torsion, cracking, deflections, etc. The use of the memetic algorithm requires its previous calibration. Each of the heuristics is run 12 times, obtaining information about the minimum and average values, as well as the scatter. The parametric study showed a good correlation for the cost, the number of strands and the steel and concrete quantities with the span length. Savings have been found between 8 and 50% compared to other structures really executed. The presented procedure allows the practical application to the real design and its adaptation to the precast process.

Experimental Performance of AFRP Concrete Bridge Deck Slab with Full-Depth Precast Prestressed Panels

While application of full-depth precast bridge deck panels may be appealing because of an accelerated construction schedule and improved safety conditions, corrosion of steel reinforcement is a major factor affecting the structural durability of precast panels and overall serviceability of a bridge deck. Herein, the concept of using aramid fiber reinforced polymer (AFRP) bars as a substitute for conventional steel reinforcement to overcome corrosion issues is verified. For this purpose, a full-scale bridge deck slab consisting of full-depth precast panels reinforced and prestressed with AFRP bars is constructed and experimentally evaluated in terms of load capacity, deformation, crack pattern, and failure mode. The precast panels are reinforced and prestressed in parallel and perpendicular to the traffic directions, respectively, and supported by reinforced concrete beams. Realistic dimensions, boundary conditions, and structural details are physically modeled to represent an actual bridge deck condition, and different concentrated load configurations including wheel and tandem axle loads are applied on both the slab interior span and overhang. The experimental results show the average failure load of the interior spans and overhangs, respectively equal to 3.9 and 1.4 times the maximum factored wheel load, where the deflection serviceability criteria are met and satisfactory deformability performance is achieved.

Long-Term Monitoring of FRP-Concrete Composite Bridge Deck for Cable-Stayed Bridges Using Optical Fiber Sensors

The Korea Institute of Construction Technology has developed a precast FRP-concrete composite deck to be applied to cable-stayed bridges. This deck is a precast structural system in which concrete is disposed at the upper part and a hollow FRP tube is disposed at the bottom to play the role of tensile reinforcement and form. This paper presents the prototype of the so-developed FRP-concrete composite deck fabricated for trial construction. Electrical resistance sensors and optical fiber sensors were installed on the prototype to evaluate its structural stability and serviceability during the 17 months of operation through a series of field loading tests. From the field loading test results, the FRP-concrete composite deck was verified to secure sufficient structural stability and serviceability along the 17 months of operation even after the repeated passage of the heavy construction trucks. Besides, it appeared also that, for long-term monitoring, the optical fiber sensor provided more reliable measurement than the electrical resistance sensor glued to the structure.

Updating and validation of the dynamic model of a railway viaduct with precast deck

This study describes the calibration and experimental validation of the dynamic model of a railway viaduct with precast deck. Global modal parameters of the structure and local modal parameters of the upper slab of the deck are identified based on a dynamic test. The calibration of the numerical model is done using a genetic algorithm that allows obtaining optimal values of 11 parameters of the numerical model. The inclusion of local modal parameters proved to be crucial, as various parameters of the numerical model do not have significant influence on global modal parameters. Mode pairing between numerical and experimental vibration modes is performed using a recent technique based on modal strain energy. The experimental validation of the calibrated numerical model is done by the comparison between numerical responses and experimental responses obtained in a dynamic test under railway traffic. This dynamic test shows the existence of a nonlinear behaviour of the viaduct's supports. There is an excellent correlation between numerical and experimental responses for different train speeds with the adjustment of the longitudinal supports stiffness of the calibrated model.

Applicability of performance improvement method of existing steel railway bridges by installing concrete decks

Steel railway bridges which exceed their design lifetime are increasing in Japan, and some of them have problems such as corrosion and fatigue. In this study, we proposed a method to improve the performance, such as the load-carrying capacity, of the existing steel railway bridges by installation of concrete decks. To figure out the applicability of the proposed method, we discussed the applicable range of span and the effect of stress reduction. Considering application into actual bridges, we proposed an installation method using pre-cast concrete decks and girder-deck connection with filler mortar and steel fasteners. Finally, we carried out loading tests of the connection with fasteners and bending tests of the applied girders. As a result, we found that the girder-deck connections have enough static capacity for lateral force and train loads, under the condition that the studs are installed and the gaps between the pre-cast decks are filled with mortar.

TINJAUAN LEBAR RETAK PADA PELAT BETON AKIBAT BEBAN STATIS

Inspection of crack width prediction procedures proposed by various investigators indicates that each formula contains a different set of variables. A literature review also suggests that there is no general agreement among various investigators on the relative significance of different variables affecting the crack width, despite the large number of experimental work carried out during the past few decades. An analytical method is developed to determine the concrete stress distribution near flexural cracks in reinforced concrete one-way slabs and used to investigate the effects of various variables on the spacing and width of cracks. The formula is developed using a large number of curvature values calculated from the concrete and steel strains at various sections between adjacent cracks for a number of composite precast deck slabs. The present method of incorporating the tension stiffening effect is verified by comparing calculated fracture mechanic and those measured by other investigators. The curvature values at sections between adjacent cracks are calculated using an empirical formula. Development of this formula is based on the curvature values calculated using the concrete and steel strains at various sections between successive cracks, for a number of slabs. Using the curvature values evaluated by the proposed formula, short-term deflections were determined for a large number of flexural members and the results were compared with those measured by other investigators. This comparison indicated that the present method of incorporating the tension stiffening effect in fracture mechanic calculations is acceptable. Keywords: crack width; formula; fracture mechanic; deflection.

격자형 강합성 바닥판의 수정된 이음부에 대한 휨성능 평가

프리캐스트 방식에 의해 제작이 가능한 격자형 강합성 바닥판의 이음부로서 콘크리트 전단키와 고장력볼트 체결로 구성된 조립식 이음부가 제안된 바 있다. 본 연구에서는 콘크리트 전단키와 고장력볼트로 구성된 이음부의 휨강성과 휨강도를 향상시키고자 단면상세를 개선하였고, 구조실험을 통해 얻은 결과를 기존 볼트체결 이음부와 비교 분석하였다. 비교분석 결과에 의하면, 전단스터드와 가외철근에 의한 이음부 콘크리트 보강으로 뚜렷한 전단균열 감소효과가 있었다. 모멘트-곡률 관계로부터 구한 휨강성을 서로 비교해 본 결과, 단면개선 전의 이음부에 비해 약 47% 정도 휨강성이 증가한 것을 알 수 있었다. 또한, 휨강도 비교결과에 의하면 개선된 이음부의 휨강도는 개선 전에 비해 약 32% 증가하였다. 개선된 이음부의 휨성능을 이음부가 없는 단면과 비교하면, 휨강도의 경우 동등 수준 이상이었으나, 휨강성의 경우는 약 37% 정도 더 작은 것으로 분석되었다. For the joint connection of the precast steel grid composite decks, the prefabricated joint which is composed of concrete shear key and high-tension bolts was already proposed. In this study, for the purpose of increasing the bending stiffness and bending strength of the proposed prefabricated joint section details of the proposed joint are modified, and through experimental tests the bending performance, such as stiffness and strength of a modified joint, is compared with those of the proposed joint. Test and analysis results show that the shear cracks in the concrete shear key are clearly reduced by the strengthening of the shear key using shear studs and additional rebars. According to analysis results of the moment-curvature relationship, bending stiffness of the modified joint is about 47% greater than the stiffness of the proposed joint. Furthermore, the modified joint has about 32% greater bending strength than the proposed joint. Compared to specimens without the joint the modified joint has same or slightly higher bending strength, but about 37% lower bending stiffness.

Tests and limit analysis of loop connections between precast concrete elements loaded in tension

This paper deals with loop connections loaded in tension. Such connections; also known as U-bar joints, are frequently used in practice to establish continuity between precast deck elements in steel–concrete composite bridges. The tensile strength of a loop connection may either be governed by yielding of the U-bars or by failure in the joint concrete. Only few investigations of the case of concrete failure can be found in the literature. This paper presents an experimental program dedicated to study loop connections critical to concrete failure. The results show that the ultimate load is influenced by important design parameters such as the overlapping length of the U-bars, the spacing between adjacent U-bars and the amount of transverse reinforcement. Knowledge about the parameters that have an effect on the failure of the joint concrete is important in order to avoid this failure mode in practice. The paper also presents an upper bound plasticity model, which is able to capture the experimental tendencies in a satisfactory manner. Finally, the paper includes discussions of how the presented research may be utilized in practice to design connections that are able to transfer the full yield strength of the connecting precast elements.

Whiteman Creek Bridge: A synthesis of accelerated bridge construction, ultrahigh- performance concrete, and fiber-reinforced polymer

The replacement of the Whiteman Creek Bridge, located in Ontario Canada, is described in this paper. Synthesizing accelerated bridge construction, ultra-high-performance concrete, and fiber-reinforced polymer reinforcement, a three-span, concrete T-beam bridge was replaced with a single-span bridge during a seven-week highway closure. Age, condition, and shear cracks in the T-beams made the replacement necessary, and prefabricated components such as precast concrete abutments, wing walls, deck elements, and steel girders were used. To enhance durability, glass-fiber-reinforced polymer (GFRP) bars were used in the top reinforcing mat of the precast concrete deck elements and in the cast-in-place concrete barrier walls; conventional black reinforcement steel was used for the bottom reinforcing mat. Ultra-high performance concrete reduced the dimensions of joints between precast concrete elements and eliminated formwork on the deck. Deck slab erection, grouting, and construction of the bridge are described, and the project timing and costs are discussed.

Construction and monitoring of a single-span bridge with precast concrete glass-fiberreinforced polymer reinforced deck panels

The Beaver Creek Bridge in Utah is a single-span crossing with access for wildlife passage. It was built in 2009 using 44 precast concrete panels reinforced with glass-fiber-reinforced polymer (GFRP) bars. In this paper, monitoring data from two panels during lifting, transport, posttensioning, and static load testing is presented. Findings from the monitoring indicate that the relative deflections between the bridge deck and the diaphragms were small. This shows that the connections between precast concrete deck panels and prestressed concrete girders provide good composite action. The live load deflections of the prestressed concrete girders during static load testing were well within allowable limits. The strains measured during lifting and in the load tests indicate that the ACI 440.1R-06 flexural design method for GFRP reinforced concrete decks can be applied to precast concrete panels, provided that lifting and handling stresses are properly designed. A cost comparison of precast concrete deck panels reinforced with GFRP bars versus steel bars indicates that the GFRP bar reinforcement is an economically viable option.